Strange compilation error


after installing everything on a new notebook (Delphi and Components) I get a strange compilation error in WebLib.TMSFNCUtils. The compiler complains about uknown Identifier "extractFileExt" in line 2746. 
e := ExtractFileExt(AFile);

I assured that sysutils is bound, also I tried changing to 

e := SysUtils.ExtractFileExt(AFile);

I also reinstalled Webcore and FNC Core. The code completion knows ExtractFileExt in these places and as the TMS Code is fine, there must be something strange with my config. Funny: Other places use ExtractFilePath and this works. The exact error message of the compiler is:

[Fehler] WEBLib.TMSFNCUtils.pas(2746): identifier not found "ExtractFileExt"

identifier not found "ExtractFileExt"
[Fataler Fehler] identifier not found "ExtractFileExt"

Any help is very apprecated, thanks.

I forgot to describe the app: It created a simpe Webcore PWA with only a FNC Grid on it, no further code.

After commenting out this one line my code compiles. As I am experimenting with the Grid I stumbled across something else strange: If I set options.keybord.enterkehandling to something different from ekhnone the compiler complains about this unknown Identifier. IAs I set it in the object inspector this is strange to me.